Your browser is no longer supported

For the best possible experience using our website we recommend you upgrade to a newer version or another browser.

Your browser appears to have cookies disabled. For the best experience of this website, please enable cookies in your browser

We'll assume we have your consent to use cookies, for example so you won't need to log in each time you visit our site.
Learn more

Alternative Energy | Floating solar farms

Cropped floating solar farm

There is something strange in the waters of a London reservoir. A 57,500m2 floating solar photovoltaic  farm on the Queen Elizabeth II Reservoir is providing Thames Water with an off-grid electricity supply.

Equivalent in size to eight football pitches, the floating energy farm near Walton-on-Thames is thought to be the largest in Europe and – with a value of £7M – is also claiming to be the largest financed floating solar farm in the world. It boasts more than 23,000 panels and has a capacity of 6.3MW, enough to power the equivalent of around 1,800 homes.

The farm provides Thames Water with its own supply of electricity for a nearby water treatment works. It contributes to Thames Water’s ambitious goal of self-generating a third of its energy by 2020 – and with a 25-year lifespan, it will continue to provide support well after that deadline.

Cropped rendering of 13.7 yamakura dam floating solar plant (credit kyocera tcl solar)

Cropped rendering of 13.7 yamakura dam floating solar plant (credit kyocera tcl solar)

Rendering of 13.7MW solar facility at Yamakura Dam, Japan

The solar farm was built under an agreement signed by Thames Water and two solar power developers Ennoviga Solar and Lightsource Renewable Energy. Thames Water first planned the project in 2011, and, although site work did not start for several years, the farm took just 16 weeks to complete, with work finishing in March 2016.

That was due in part to a clever construction schedule – the farm was assembled in sections on land. Each time a new section was attached, the others were pushed out into the reservoir, meaning that no problematic construction on water was required.

OST Energy, an engineering and technical consultancy advising on commercial and technical risk for renewable projects, worked to secure investment from the Royal Bank of Scotland (RBS) for the floating solar farm.

Water companies might not have a lot of land to build on, but they have a lot of reservoirs

Simon Turner, OST

Part of this work included identifying the risks inherent in building and operating the farm, including one rather obvious issue.

“Water and electricity don’t mix very well,” says OST Energy director and co-founder Simon Turner. Using solar panels on water was a hard sell to investors.

Anchoring presented another issue. The farm covers around one tenth of the reservoir, which has a perimeter of 4.3km and surface area of 128.3ha, leaving plenty of room for it to drift off to a new destination. Each reservoir needs a different type of anchoring to secure it to the reservoir floor depending on its composition, meaning that a one-size-fits-all approach was unfeasible. An offshore wind specialist was consulted to make sure the farm would not move when the wind blows. As the farm has 177 anchors, it seems unlikely that this will be a problem.

So why put a solar energy farm on water at all?

“Water companies might not have a lot of land to build these on, but they have a lot of reservoirs,” says Turner.

12,000 panels

Indeed, water company United Utilities created a £3.5M floating solar farm on the Godley reservoir in Hyde, Greater Manchester, in 2015. With 12,000 panels, this farm provides United Utilities’ water treatment works with around a third of their energy requirements.

But it is not just water companies that can benefit from floating solar farms. When connected to the National Grid, a floating farm can support electricity demand too. So will they catch on?

Turner is unconvinced. “It’s quite a niche development,” he says.

“It’s not appropriate for everywhere, especially where land isn’t a premium. It’s an added layer of complication that you might not need to bother with.”

Premium land

But in places where land is at a premium, it makes sense to use all the space at a developer’s disposal – including the surface of a reservoir.

In Japan, floating solar farms are helping solve the problem of limited land availability. Solar energy company Kyocera has installed several farms, with three – respectively 1.2MW, 1.7MW and 2.3MW in size – completed in 2015.

But the company’s most ambitious floating solar farm to date is a planned 13.7MW facility on the Yamakura Dam Reservoir. Once finished the farm will cover 180,000m2 and produce an estimated 16,170MWh per year — enough electricity to power approximately 4,970 homes. Construction of the 51,000 module farm started in December 2015 and is scheduled to finish early 2018.

Side effect

Brazil is benefiting from a useful side effect of these floating farms. The country uses hydroelectricity as part of its energy mix, but the powerful Brazilian sun has a tendency to reduce the reservoirs to alarmingly low levels through evaporation, thereby affecting the reliability of its hydroelectric generating capability.

Floating solar farms can reduce  evaporation as they shield part of a reservoir’s surface from the sun. Research and development projects are underway to establish the possibility of rolling out floating solar farms in Brazil.

Two prototype floating farms were installed in Brazil in early 2016, on the Sobradinho Reservoir and the reservoir at the controversial Balbina Dam which has struggled to deliver its hydro power capacity.

Reduced hydro-electric dependency

Balbina’s reservoir experiences severe drought, meaning that the dam is only able to generate one fifth of its 250MW operating capacity so solar power is a way of reducing dependence on hydro electricity from the reservoir.

To begin with, each farm will have 1MW of capacity.  But in October this will be increased to 5MW, with tests on the floating panels due to finish in early 2019. Once this stage is complete it is hoped that Balbina’s floating farm will be scaled up to 300MW, enough to power 540,000 homes.

With their relative ease of construction and the solutions they bring, it is unsurprising that floating solar farms are appearing as a sub-section of the wider solar market.

Developing nations

Globally, it appears to be a good time for solar energy. A report published by Climatescope – a clean energy country tracker – in December showed that developing nations are overtaking wealthier countries on clean energy leadership. A key group of emerging markets produced 18% more renewable capacity than  Organisation for Economic Co-operation and Development countries in 2015, says the report.

There was also good news for solar energy in the report. Investment in utility-scale solar energy in the countries surveyed soared 43% to £58.1bn, and in some nations solar power innovations can now compete against – and beat – fossil fuel projects on price.

However, the news did highlight the fact that renewables investment in wealthier countries appears to have levelled out.

As Turner explains, globally all renewables appear to be growing rapidly within the last 10 years. But that success masks some turmoil.

Government support

“Underneath that great growth, you are still reliant on government support,” he says.

There have been significant changes to UK government subsidies over the past 18 months. There were 15 government policy changes impacting renewables from May 2015 to April 2016, with several unexpected in the industry.

One significant difference will apply from March, when the subsidy regime for renewables changes.

“We’ve had massive growth in the last few years but next year, after March, there won’t be really any large-scale projects built,” says Turner.

“So globally yes, it’s growing, but [in] individual countries – it is lumpy.”


According to Turner, the market should level out solar is able to compete more equally with mainstream electricity sources. So did the government pull its support too early?

“If you’re not worried about the politics and you’re just looking at the economics of it working, then yes, it is slightly too early,” he says, although he admits there are other factors to consider in the decision.

When changes to subsidies were announced in December 2015, the government stressed that they were always intended to be temporary measures and that revisions were to ensure bill payers received value for money.

Despite the challenges, projects like the Queen Elizabeth ll Reservoir floating solar farm show that bold ideas continue to thrive in the sector.



Have your say

You must sign in to make a comment

Please remember that the submission of any material is governed by our Terms and Conditions and by submitting material you confirm your agreement to these Terms and Conditions. Please note comments made online may also be published in the print edition of New Civil Engineer. Links may be included in your comments but HTML is not permitted.